Exclusive: We tested over half a dozen of this year's flagship phones and found that the LG V40 is the best at maintaining a connection.

Your mobile phone is connected. Or, at least, it should be. Whether you make lots of calls or just scroll through your Instagram feed, staying online with your carrier's LTE network is absolutely critical. And while this year's flagship phones all perform pretty well at that basic task, the LG V40 takes the crown as the best.

We've been working with Cellular Insights for a few years now to periodically test the RF reception on each year's leading smartphones, as those tests require specialized lab equipment we don't have in PC Labs.

For this year's RF testing, we included a whole bunch of recent phones. We've collected results from the iPhone XS, XS Max, and XR; the Samsung Galaxy Note 9; the Google Pixel 3; the LG V40; and the OnePlus 6T. From last year, we have data on the iPhone X, the Google Pixel 2, the LG V30, and the Samsung Galaxy Note 8 as well.

All of the Android phones we tested this year have Qualcomm's new X20 modem, which promises up to 1.2Gbps speeds. On paper, that's superior to the Intel XMM7560 in today's iPhones, which offers speeds of up to a gigabit. Curious about previous test results? See:

Realistically, though, no US carrier can achieve the X20's maximum speeds. The X20 allows for 12 data streams of 100Mbps each. A 20MHz LTE channel with two spatial streams (2x2 MIMO) accounts for two 100Mbps streams; a 4x4 MIMO carrier accounts for 4. Right now in North America, only the Bell network in Canada (which is also used by Telus customers) can achieve 12 streams.

Our lab tests look at performance with a single 20MHz LTE channel—so, up to 4 streams. We're looking for sensitivity as the signal fades, not the absolute maximum speed that can be pumped through a modem.

We saw R&S's solution recently at Mobile World Congress Americas and we were blown away by its power and flexibility. The CMWFlexx can simulate pretty much any signal condition you can think of, including arcane band combinations, signal handoffs, and even 5G. It's used by both handset makers and wireless carriers to test and verify their phones.

It's a Tight Race

For most levels of signal, there isn't a huge difference between this year's premium smartphones. Putting five models on this chart makes it a bit hard to read; the major takeaway is that the OnePlus 6T is a notch slower than more expensive phones with very good signal, but recovers in weak-signal conditions.

In the brutal world of modem manufacturer bragging rights, Qualcomm stays in the lead, but just barely. The LG V40 has the best performance of any of the Qualcomm-powered phones we saw, overall. The iPhone XS Max has the best performance of any of the Intel-powered units. This chart shows that they're pretty much neck and neck. I'd call the race for Qualcomm, though, because it both maintains its fastest speeds longer and manages to eke out a bit more speed in very low-signal conditions.

If you have an older phone, will buying a newer model improve your speeds? Here's where lab test results become different from real-world results. Our lab tests check to see how phones deal with a single, 20MHz carrier of Band 4 signal. Qualcomm has been doing pretty well at that for the past few years, since it helped usher in 4x4 MIMO phones, which can use four antenna branches. On this chart of this year's and last year's Samsung and Google phones, you see that the Galaxy Note 9 pulls ahead a tiny bit from time to time, but everything's pretty much at par.

But new phones have a lot more differences than the speeds that they can support on one 20MHz channel. Each year, companies add new frequency bands that older phones don't support. For example, this year's iPhones include T-Mobile's Band 71, which extends coverage into areas where older iPhones would find none. AT&T phones with LTE Band 30 can speed along in urban areas where other AT&T phones may hit congestion.

Newer modems can also support more data streams, and more carriers, at once. The Qualcomm X20 modem's 12 streams follow last year's X16's 10 streams, and the X12 modem's six streams. So we turned to the crowdsourced results provided by our sister company Ookla Speedtest. (Ookla is owned by Ziff Davis, PCMag.com's parent company.) This chart shows the difference on US networks between Samsung Galaxy Note 9 phones, with the X20 modem; Galaxy Note 8s, with the X16; and Galaxy Note 5s, with an older Samsung Exynos modem. As you can see, it's significant.

So while the LG V40 may get this year's crown for best signal reception, any new flagship phone is going to get better coverage and speeds than a phone a few years old.

About the Author

PCMag.com's lead mobile analyst, Sascha Segan, has reviewed hundreds of smartphones, tablets and other gadgets in more than 9 years with PCMag. He's the head of our Fastest Mobile Networks project, one of the hosts of the daily PCMag Live Web show and speaks frequently in mass media on cell-phone-related issues. His commentary has appeared on ABC, the BBC, the CBC, CNBC, CNN, Fox News, and in newspapers from San Antonio, Texas to Edmonton, Alberta.

Segan is also a multiple award-winning travel writer, having contributed to the Frommer's series of travel guides and Web sites for more than a decade. Other than his home town of New York, his favorite ... See Full Bio